Family resemblance for qualitative and quantitative traits is being studied by two methods: generalized path analysis of pairs of biological and social relatives (Rao) and segregation analysis of nuclear families under a mixture of a major locus with polygenes (MacLean). Both models include common environment and dominance. High power to resolve major loci and to separate genes from common environment has been demonstrated. These methods should bring increased precision to/recurrence risks for family planning.